Living By Chemistry SECOND EDITION Unit 4 TOXINS
Living By Chemistry SECOND EDITION Unit 4: TOXINS Stoichiometry, Solution Chemistry, and Acids and Bases
Lesson 82: Holey Moley Preparing Solutions
Chem. Catalyst Imagine that you want to make 5 L of 0. 60 M Na. Cl solution for a saltwater aquarium. You need to determine the correct mass of Na. Cl needed to obtain the correct concentration, or the fish will die. a. What information do you have? b. What information do you need?
Key Question How can you make a solution with a specific molarity?
You will be able to: • calculate the amounts necessary to create a solution with a desired volume and molarity • determine the number of grams of solute in a sample with a specific volume and molarity
Prepare for the Lab Work in groups of four.
Discussion Notes You can use a hydrometer to measure the density of a solution. The 0. 60 M solution comes closest to resembling ocean water. There are several possible sources of error in this experiment.
Discussion Notes (cont. ) Molarity relates moles and liters. Molarity = moles/liters If you know the molarity of a solution and the size of the sample, you can calculate the number of grams of substance dissolved in that solution. Grams = moles • molar mass
Wrap Up How can you make a solution with a specific molarity? • In order to calculate the amount of solute needed to make a solution with a certain molarity, you must use the molar mass of the solute to convert moles to mass. • Solutions of specific concentrations can be made by weighing out the appropriate amount of the substance dissolved in the solution. • If you know the molarity and volume of a sample of solution, you can figure out the mass of the dissolved substance in that sample.
Check-In How many grams of salt are in 0. 100 L of 2. 50 M Na. Cl?
- Slides: 10